After thinking about the Shannara series and other fantasy settings I've read, it's actually fairly grimdark at times. It lacks constant murder/swearing/sex like Game of Thrones, but some of the novels are just straight up dark/depressing shit with death happening all the time. The Elf Queen of Shannara, for example, is one of the most over the top when it comes to just having a dark, evil ass setting. Island that the elves move to that they start using ancient magic to alter the local wildlife, turns sour and demons and shit start coming out of the woodwork, and their modified creations become constant threats to them. They sit behind their walls and just wait while time runs out. Not to mention that there's a couple of big reveals about the origin of the Shadowen, and many of the main/supporting characters die in pretty grisly fashion. Like, it doesn't even end on a good note, it's just one long downer for Wren hah.
That was, on further rememberance, a pretty rough book for an 11 year old.
edit: HAH, haven't read the book in over 20 years, just remembered that the island was called Morrowindl and has a giant volcano at the center of the island. Good work, Bethesda!